SQL 为过去一周的每一天创建的记录数返回零答案

【问题标题】：SQL returns zero for number of records created in each day of past weekSQL 为过去一周的每一天创建的记录数返回零
【发布时间】：2019-12-31 09:04:45
【问题描述】：

我正在编写这个 SQL 查询，它计算过去 7 天内每天添加到表中的记录数。它应该返回第 1 天的 x 条记录，第 2 天的 y 条记录，依此类推。这是我的查询；

select h.hr, count(e.eventID) as cnt
from ( select 0 hr union all 
       select 1 union all 
       select 2 union all 
       select 3 union all 
       select 4 union all
       select 5 union all 
       select 6 
     ) h left join 
     ( select * 
       from events e 
       where e.timeStamp >= cast(now() as date)
     ) e 
    on day(e.timeStamp) = h.hr
group by h.hr

问题是，当它应该返回记录数时，它在所有 7 天内返回值 0。我哪里错了？

我的数据集：

+---------+----------+---------------------+---------------------+
| eventID | personID | timeStamp           | dateModified        |
+---------+----------+---------------------+---------------------+
|       1 |        8 | 2019-12-28 12:26:49 | 2019-12-28 12:26:50 |
|       2 |        0 | 2019-12-28 12:26:51 | 2019-12-28 12:26:52 |
|       3 |        0 | 2019-12-28 12:27:11 | 2019-12-28 12:27:12 |
|       4 |        0 | 2019-12-28 12:27:12 | 2019-12-28 12:27:12 |
|       5 |        0 | 2019-12-28 12:28:20 | 2019-12-28 12:28:20 |
|       6 |        0 | 2019-12-28 12:28:21 | 2019-12-28 12:28:21 |
|       7 |        0 | 0000-00-00 00:00:00 | 2019-12-28 12:28:21 |
|       8 |        2 | 2019-12-28 12:30:02 | 2019-12-28 12:30:02 |
|       9 |        0 | 2019-12-28 12:30:03 | 2019-12-28 12:30:03 |
|      10 |        1 | 2019-12-30 05:38:02 | 2019-12-30 05:38:01 |
|      11 |        0 | 2019-12-30 05:38:05 | 2019-12-30 05:38:03 |
|      12 |        0 | 2019-12-30 05:41:42 | 2019-12-30 05:41:41 |
|      13 |        1 | 2019-12-30 05:41:41 | 2019-12-30 05:41:41 |
|      14 |        1 | 2019-12-30 05:43:11 | 2019-12-30 05:43:11 |
|      15 |        0 | 2019-12-30 05:43:13 | 2019-12-30 05:43:11 |
|      16 |        8 | 2019-12-30 05:44:08 | 2019-12-30 05:44:08 |
|      17 |        0 | 2019-12-30 05:44:10 | 2019-12-30 05:44:08 |
|      18 |        1 | 2019-12-30 05:48:06 | 2019-12-30 05:48:06 |
|      19 |        0 | 2019-12-30 05:48:08 | 2019-12-30 05:48:07 |
|      20 |        1 | 2019-12-30 06:09:58 | 2019-12-30 06:09:57 |
|      21 |        0 | 2019-12-30 06:10:00 | 2019-12-30 06:09:58 |
|      22 |        0 | 2019-12-30 06:11:22 | 2019-12-30 06:11:20 |
|      23 |        1 | 2019-12-30 06:11:20 | 2019-12-30 06:11:20 |
|      24 |        1 | 2019-12-30 06:13:30 | 2019-12-30 06:13:30 |
|      25 |        0 | 2019-12-30 06:13:32 | 2019-12-30 06:13:30 |
|      26 |        0 | 0000-00-00 00:00:00 | 2019-12-30 06:13:42 |
|      27 |        0 | 0000-00-00 00:00:00 | 2019-12-30 06:14:00 |
|      28 |        1 | 2019-12-30 06:14:55 | 2019-12-30 06:14:54 |
|      29 |        0 | 2019-12-30 06:14:57 | 2019-12-30 06:14:55 |
|      30 |        0 | 0000-00-00 00:00:00 | 2019-12-30 06:14:59 |
|      31 |        8 | 2019-12-30 06:16:22 | 2019-12-30 06:16:22 |
|      32 |        0 | 2019-12-30 06:16:24 | 2019-12-30 06:16:22 |
|      33 |        0 | 0000-00-00 00:00:00 | 2019-12-30 06:16:27 |
|      34 |        8 | 2019-12-30 06:17:56 | 2019-12-30 06:17:56 |
|      35 |        0 | 2019-12-30 06:17:58 | 2019-12-30 06:17:56 |
|      36 |        1 | 2019-12-30 06:18:32 | 2019-12-30 06:18:31 |
|      37 |        0 | 2019-12-30 06:18:33 | 2019-12-30 06:18:31 |
|      38 |        0 | 0000-00-00 00:00:00 | 2019-12-30 06:18:37 |
|      39 |        8 | 2019-12-30 06:21:23 | 2019-12-30 06:21:23 |
|      40 |        0 | 2019-12-30 06:21:25 | 2019-12-30 06:21:23 |
|      41 |        0 | 2019-12-30 06:21:33 | 2019-12-30 06:21:32 |
|      42 |        0 | 2019-12-30 06:21:34 | 2019-12-30 06:21:32 |
|      43 |        1 | 2019-12-30 06:39:58 | 2019-12-30 06:39:57 |
|      44 |        0 | 2019-12-30 06:40:00 | 2019-12-30 06:39:59 |
|      45 |        1 | 2019-12-30 06:40:29 | 2019-12-30 06:40:29 |
|      46 |        0 | 2019-12-30 06:40:31 | 2019-12-30 06:40:29 |
|      47 |        1 | 2019-12-30 06:42:06 | 2019-12-30 06:42:05 |
|      48 |        0 | 2019-12-30 06:42:07 | 2019-12-30 06:42:05 |
|      49 |        1 | 2019-12-30 06:44:21 | 2019-12-30 06:44:20 |
|      50 |        0 | 2019-12-30 06:44:22 | 2019-12-30 06:44:21 |
|      51 |        1 | 2019-12-30 06:45:35 | 2019-12-30 06:45:34 |
|      52 |        0 | 2019-12-30 06:45:36 | 2019-12-30 06:45:34 |
|      53 |        1 | 2019-12-30 06:46:27 | 2019-12-30 06:46:27 |
|      54 |        0 | 2019-12-30 06:46:28 | 2019-12-30 06:46:27 |
|      55 |        1 | 2019-12-30 06:50:40 | 2019-12-30 06:50:39 |
|      56 |        0 | 2019-12-30 06:50:41 | 2019-12-30 06:50:39 |
|      57 |        8 | 2019-12-30 08:10:52 | 2019-12-30 08:10:57 |
|      58 |        0 | 2019-12-30 08:10:59 | 2019-12-30 08:10:58 |
|      59 |        1 | 2019-12-30 09:47:06 | 2019-12-30 09:47:07 |
|      60 |        0 | 2019-12-30 09:47:08 | 2019-12-30 09:47:07 |
|      61 |        1 | 2019-12-30 11:43:17 | 2019-12-30 11:43:17 |
|      62 |        0 | 2019-12-30 11:43:18 | 2019-12-30 11:43:18 |
|      63 |        1 | 2019-12-30 11:43:35 | 2019-12-30 11:43:35 |
|      64 |        0 | 2019-12-30 11:43:36 | 2019-12-30 11:43:35 |
|      65 |        1 | 2019-12-30 11:44:05 | 2019-12-30 11:44:05 |
|      66 |        0 | 2019-12-30 11:44:06 | 2019-12-30 11:44:06 |
|      67 |        1 | 2019-12-30 12:26:47 | 2019-12-30 12:26:47 |
|      68 |        0 | 2019-12-30 12:26:49 | 2019-12-30 12:26:48 |
|      69 |        0 | 2019-12-30 12:40:34 | 2019-12-30 12:40:33 |
|      70 |        1 | 2019-12-30 12:40:33 | 2019-12-30 12:40:34 |
|      71 |        8 | 2019-12-31 04:52:29 | 2019-12-31 04:52:28 |
|      72 |        0 | 2019-12-31 04:52:31 | 2019-12-31 04:52:29 |
|      73 |        0 | 2019-12-31 04:53:50 | 2019-12-31 04:53:47 |
|      74 |        8 | 2019-12-31 04:53:48 | 2019-12-31 04:53:47 |
|      75 |        8 | 2019-12-31 04:54:14 | 2019-12-31 04:54:13 |
|      76 |        0 | 2019-12-31 04:54:16 | 2019-12-31 04:54:14 |
|      77 |        8 | 2019-12-31 04:54:40 | 2019-12-31 04:54:38 |
|      78 |        0 | 2019-12-31 04:54:41 | 2019-12-31 04:54:39 |
|      79 |        0 | 2019-12-31 04:55:11 | 2019-12-31 04:55:09 |
|      80 |        8 | 2019-12-31 04:55:10 | 2019-12-31 04:55:10 |
+---------+----------+---------------------+---------------------+

【问题讨论】：

什么是h.hr？小时？
@tcadidot0 我为类似任务创建了一个包含 1-23 值的小时表。我将前 7 行用于左关节，以便在没有创建记录的日子里输出零。
你每天都在工作吗？
不，从技术上讲，小时是一个数字表，所以如果我使用它的前 7 行，结果应该是一样的吧？
这有点不对劲吗？ e.timeStamp >= cast(now()

标签： mysql sql database mariadb

【解决方案1】：

您没有将数字表与您的数据集正确连接。

我认为你想要：

select d.dy, count(e.eventID) as cnt
from ( select 0 dy union all 
       select 1 union all 
       select 2 union all 
       select 3 union all 
       select 4 union all
       select 5 union all 
       select 6 
     ) d 
left join events e
     on e.timestamp >= current_date - interval d.dy day
     and e.timestamp < current_date - interval (d.dy - 1) day 
group by d.dy

注意：我将子查询重命名为d(dy)，这样它的目的就更清楚了。

【讨论】：

【解决方案2】：

你应该使用

DAYOFWEEK()

函数，所以你的查询就像

SELECT DAYOFWEEK(e.timeStamp), 
count(EventId) from events where 
e.timeStamp >= DATE(CURDATE) - INTERVAL 7 DAY
group by DAYOFWEEK(e.timeStamp)

ps：我现在不能尝试，但它应该可以工作。

【讨论】：